ABSTRACT
Figure 26.2 shows the radiant energy peak as a function of temperature in the LWIR. It is important to note that the difference between the blackbody curves is the “signal” in the infrared bands. For an infrared sensor, if the background temperature is 300 K and the object of interest temperature is 302 K, the signal is the 2 K difference in flux between these curves. Signals in the infrared ride on very large amounts of background flux. This is not the case in the visible. For example, consider the case of a white object on a black background. e black background is generating no signal, while the white object is generating a maximum signal assuming the sensor gain is properly adjusted. e dynamic range may be fully utilized in a visible sensor. For the case of an IR sensor, a portion of the dynamic range is used by the large background flux radiated by everything in the scene. This flux is never a small value; hence sensitivity and dynamic range requirements are much more dicult to satisfy in IR sensors than in visible sensors.
